Organic disulfides are a class of important industrial chemicals which can be used in the manufacture of pesticides, rodent repellants, and insecticides, as intermediates for synthesis of pharmaceuticals, and as additives in greases and fuels. High molecular weight organic disulfides can also be used as additives in the plastic industry as chain terminating agents in polymerization processes.
The production of organic disulfides is well known in the art. However, the processes currently available for producing organic disulfides, especially lower alkyl disulfides, are so tedious and expensive that the production costs remain relatively high thereby preventing real commercial development. For example, alkyl disulfides such as diethyl disulfide can be prepared from ethyl mercaptan by forming sodium ethanethiolate in either water or alcohol solution followed by oxidizing the sodium ethanethiolate with oxygen. However, the oxygen consumption is high thereby adding cost to the disulfide product. Furthermore, the yield of some organic disulfides by oxygen oxidation is generally 85% or less.
Organic disulfides can also be prepared by oxidizing mercaptans using water-soluble persulfates, perchlorates, or permanganates. However, acids are required if the oxidizing agents are perchlorates or permanganates. Additionally, the quantity of the oxidizing agents is high, generally 1 mole of oxidizing agent per 2 moles of mercaptan, in order to obtain a good yield. Use of high quantities of oxidizing agents and acids further increases manufacturing costs of organic mercaptans.
It has also been reported that mercaptans or metal salts of mercaptans can be oxidized by hydrogen peroxide in the presence of an acid. Again, such a process requires the addition of an acid thereby increasing the manufacturing costs of organic disulfides.
Therefore, there is an ever-increasing need for developing an improved and simple process for producing organic disulfides. Development of a simple process for producing organic disulfides would also significantly contribute to the art. Because the market for organic disulfides is growing larger, seemingly small improvement translates into a significant savings in manufacturing costs.